Actuators for casement sash.
Casement sash, within which are included vertically hinged and horizontally or awning hinged sash, can be opened and closed with cables, as suggested in PCT Publication PCT/AU98/00982. This reference addresses a problem requiring a large pulling force to initiate sash opening when hinge bars for a sash are approximately aligned along a direction of cable pull.
If a cable actuator uses a fixed mechanical advantage from application of motive torque to a shaft the operator can be required to apply substantially increased torque during initial sash opening and then lessened torque during further sash opening. If the mechanical advantage is increased to lessen the initial torque required, then further opening of the sash requires excessive revolutions of the torqued shaft.
The PCT reference proposes a cable actuator solution to this problem. The solution involved sliding a wedge along a hinge track to engage and initiate opening movement of a hinge bar. The invention of this application proposes other solutions also implemented by cable actuators.
I have devised ways of arranging a casement sash cable actuator so that tensioning an opening pull cable moves the cable from an elongated to a tensioned path in a way that causes initial opening movement of the sash. The cable movement that initiates sash opening applies an increased mechanical advantage during initiation of sash opening when the opening pull cable moves from one path to another. Thereafter, a reduced mechanical advantage applied by a cable winder further opens the sash. This allows an operator to initiate sash opening by using torque no larger than is required for further opening of the sash. The actuator also allows the further sash opening to proceed with only a few turns of applied torque.
My cable actuator achieves these features by using a cable engager that engages an opening pull cable when the sash is closed.
When the opening pull cable is tensioned to open a sash from a closed position, the cable moves the cable engager in a way that initiates sash opening. The cable engager can be a projection fixed to the sash or its hinge bars in a position that is appropriate for engaging the cable, or it can be a pivot arm that the opening pull cable moves to open the sash. In either case, the cable engager forces the opening pull cable into a path that is longer than a tensioned path assumed by the opening pull cable to initiate sash opening. Then as the opening pull cable is tensioned and moves toward the shorter tensioned path, it moves the cable engager away from the elongated path in a way that urges the sash open from a closed position. In effect, such an arrangement applies additional mechanical advantage to the first few degrees of opening of the sash, whereupon the cable actuator proceeds with further opening of the sash at a lesser mechanical advantage.